JP2004532683A - Collection device - Google Patents

Abstract

A collection device for collecting a sample tissue or a foreign substance from a subject through an opening or a small incision is provided.
An endoscopic surgical device for recovering cut tissue or foreign matter from within a subject is disclosed. The apparatus includes a support unit and a tissue retrieval net system. The net system is carried by the support unit and is inserted into the subject through an opening or small incision and is operated to retrieve tissue that has been cut in a conventional manner. The net system includes a net, a net actuator, and a net deployment and retrieval assembly that transmits motion between the net and the actuator. The net system further includes at least one net connector positioned such that there is only one connector within the joint area defined by the sharp bend location of the device during operation.
[Selection diagram] Fig. 1

Description

【Technical field】
[0001]
Cross reference to related application
This PCT application claims the benefit of a United States non-provisional patent application filed May 15, 2002, entitled "Recovery Device," which was subsequently filed on May 5, 2001, under the title "Recovery Device." Claims the benefit of US Provisional Application No. 60 / 292,168, filed on Aug. 18
[0002]
Field of the invention
The present invention relates to surgical devices, and more particularly to an endoscope retrieval device configured to retrieve a relatively small piece of sample tissue or foreign material from a human subject through an opening or small incision.
[Background Art]
[0003]
Background of the Invention
Snares, baskets, and graspers are widely used to cut, capture, and retrieve tissue samples and foreign material from within a subject. The device has been used in human and animal subjects in laparoscopic surgery and other procedures where access into the subject is only possible through a small opening. One exemplary use is intestinal polyp resection and retrieval, where a wire snare is passed through a colonoscope instrument channel, surrounds the intestinal polyp, and clamps around the polyp to cut the polyp. The cut polyps are collected into a net inserted through the instrument channel. The net is manipulated to wrap the polyp, and then withdrawn with the device so as not to disturb the structure of the tissue.
[0004]
In this and other procedures, the net and snare must be very small in order to be passed through the instrument channel or other passageway within the subject. Prior art proposals use a snare supported in a plastic tube that is meandered into a subject to position the snare at a desired location. The snare is then deployed from the tube, manipulated to excise the polyp, and collected in a tube for removal from the subject.
[0005]
A net collapsed in another tube is introduced through the instrument channel or the like to remove the polyp. In the vicinity of the target polyp, the net is deployed like a snare and manipulated to catch the polyp. The net is then closed sufficiently to confine the polyp and is withdrawn from the subject.
[0006]
Junker U.S. Patent No. 5,643,283, which is hereby incorporated by reference in its entirety, discloses an apparatus for retrieving an object from within a subject. The device includes a shaft and a compressible bladder for retrieving an object located proximate a distal end of the shaft. The bag includes a mouth that can be opened and closed. The bladder is held by a slidable tether over a cable loop near the distal end of the shaft. The net slides freely on the cable loop to form a bladder at the distal end of the shaft. The tether is secured at a second position near the proximal end of the shaft, and in one embodiment, is tied to a ring and tied with heat shrink tubing. When the target foreign body is in the bag, the clinician separates the handle ring and closes the net around the object. The clinician then removes the device from the patient and removes the object from the net. The clinician then places the ring on a post to pack the bladder into the distal end of the shaft.
[Patent Document 1]
U.S. Pat. No. 5,643,283
DISCLOSURE OF THE INVENTION
[Problems to be solved by the invention]
[0007]
Several problems are encountered in the operation of the commercial embodiment of U.S. Pat. No. 5,643,283. Clinicians experience difficulties in understanding the operation of the tether, particularly the interaction of the ring and post. The ring should be used to pull the net into the shaft only when no object is in the net. In preparation for capturing an object, the ring is separated to open the net. The net is then slid over the target object and the net is closed. At this point, the appropriate action is simply to remove the device from the patient. However, when operating the device, some clinicians further attempt to retract the net into the shaft as the net is bundled at the distal end of the cable loop. This can entangle the net or, in some cases, damage the tube. Occasional improper operation of the device sometimes causes permanent malfunction.
[0008]
The commercial aspects discussed above also add undesirable costs to the product. In particular, tether and heat shrink operations over the entire length add material and assembly labor costs to the equipment.
[0009]
The present invention provides a new and improved retrieval device constructed and arranged such that movement of the net during opening and retrieval is not extremely restricted. The tie net attachment is secure, and it provides convenient net stuffing in the introducer passage. The device provides a convenient and economical method of sample collection during endoscopic procedures. The new collection device is easy to assemble, is cheaper to manufacture, and is easy to use by end consumers.
[Means for Solving the Problems]
[0010]
Summary of the Invention
In one illustrated aspect of the invention, there is provided an endoscopic surgical device for recovering cut tissue from within a human subject. The device includes a support unit and a tissue retrieval net system.
[0011]
The support unit includes a body and an elongated introducer member. The body defines a first passage through the body. The introducer member has a first end proximal and fixed to the body, and a second end remote from the body. The introducer member further defines a second passage aligned with the first passage and open at the second end.
[0012]
The tissue retrieval net system includes a net, a net deployment and retrieval assembly, and a net actuator system.
[0013]
The net includes a wire-like elastic loop and a net element having a mouth and a tissue collection bag slidably disposed on the loop. The loop terminates in two parallel loop cables. The net is positioned proximate the second end for deployment and contraction through the opening of the second passage.
[0014]
The net deployment and retrieval assembly extends substantially through the first and second passages and connects to the net. The assembly includes a motion transmitting member extending into the second passage to the loop.
[0015]
The net actuator unit includes a first handle fixed to the main body, and a second handle fixed to the motion transmitting member and movable with respect to the first handle. The act of moving the second handle relative to the first handle moves the net into and out of the opening of the second passage.
[0016]
The second passage of the introducer member has a diameter, when deployed, substantially less than the width of the loop. The member engages the loop at the opening at the second end and resiliently collapses and expands the loop as the net contracts and moves into the passage of the introducer member. The loop resiliently returns to its uncollapsed shape when deployed.
[0017]
In one aspect, the net system includes at least one connector adapted to fasten each loop cable. An end of the net element is tied to the motion transmitting member proximal to the at least one connector with respect to the support unit.
[0018]
In a second aspect, the net system further comprises a first connector, a second net connector proximate an opening of the second passage, and the loop cable between the first connector and the second connector. And an intermediate portion defined by the axial distance of The first connector and the second connector are adapted to fasten each loop cable. The end of the net element is tied to the loop in an intermediate loop between the first connector and the second connector.
[0019]
The deployment and retrieval assembly may include a thin, flexible wire-like motion transmitting member between the net actuator unit and the loop. The motion transmitting member extends within the introducer guideway, which closely surrounds the motion transmitting member and forces the member to translate axially within the passage.
[0020]
The first connector may be located at least 6 inches from the second connector such that during deployment of the net element, only one connector is in the articulated area.
[0021]
An end of the net element may be tied to the motion transmitting member proximate a shoulder proximal of the connector with respect to the support unit.
【The invention's effect】
[0022]
The present invention offers advantages over the devices available in the prior art. In a second aspect, the net is secured distally and proximally through the use of first and second connectors. The connectors are spaced sufficiently to provide a tie net attachment without the use of additional tether mechanisms. The connectors are positioned so that there can be only one at a time in the joint area of the endoscope, allowing for easy net deployment in a variety of geometric manipulation shapes.
[0023]
In a first aspect, only one connector is used to tie the proximal side of the net. This technique reduces the amount of cable loop length in the joint area. The reduction in cable loop length simultaneously reduces the amount of rigid material in the joint area of the endoscope, and also allows for easy net deployment in various geometric manipulation arrangements.
[0024]
The device is also easier to assemble and less expensive to manufacture than certain conventional designs.
[0025]
Further features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings.
BEST MODE FOR CARRYING OUT THE INVENTION
[0026]
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a front view of a surgical device constructed in accordance with one aspect of the present invention, illustrating a deployed net element;
FIG. 2 is a view similar to FIG. 1 illustrating the contracted net element;
FIG. 3 is a partially enlarged view of a portion of the apparatus shown in FIG. 1 showing details of the introducer member;
FIG. 4 is a partial enlarged view of a portion of the device illustrated in FIG. 1, depicting the device in an illustrative shape within a subject;
FIG. 5 is a partial enlarged view of a portion of a surgical device constructed in accordance with the second aspect of the present invention, showing details of the introducer member;
FIG. 6 is a partially enlarged view of a portion of the device illustrated in FIG. 5, depicting the device in an illustrative shape within a subject.
[0027]
Best mode considered for carrying out the invention
An endoscopic surgical apparatus 10 for recovering cut tissue and / or foreign matter from within a subject is illustrated in the drawings. With reference to FIGS. 1 and 2, in one embodiment, the device 10 includes a support unit 12 and a tissue retrieval net system 16. The net system is carried by the unit 12 and inserted into the subject through an opening or small incision and operated to retrieve tissue samples previously separated from the subject by conventional methods, eg, a snare / cautery system. I can do it. Accordingly, the net system 16 includes a net 20, a net actuator 24, and a net deployment and retrieval assembly 28 that transmits motion between the net and the actuator 24. The net 20 includes a net element 21 and a net loop 22 as well as a distal 25 and a proximal knot suturing the net.
[0028]
The device 10 can be used with any suitable or conventional endoscopic or laparoscopic surgical equipment. For the purposes of this disclosure, the device 10 will be described for use with an endoscope / colonoscope / sigmoidoscopy-type instrument (hereinafter also referred to as a scope: not shown) in a conventional or suitable configuration. The scope includes an elongated body having a controllably flexible protruding end region. A surgical instrument such as device 10 can be introduced through an instrument channel extending through the scope body to retrieve tissue targeted by a surgeon operating the scope.
[0029]
The support unit 12 supports the net system 16 so that the net 20 can be inserted by the surgeon through the instrument channel of the scope. The support unit 12 includes a body 30 defining a passage, an elongate introducer 40 having a first end 42 proximal and fixed to the body 20 and a second end 44 remote from the body. including. The introducer 40 is tubular and is aligned with the body passage to accommodate the net system.
[0030]
The illustrated introducer 40 can snake into the subject through the instrument channel of the scope, and can easily be brought into any shape required when the scope body is flexed by the surgeon. It is a smooth and flexible member that can be bent. In the embodiment shown, introducer 40 is generally a cylindrical small diameter tube formed from a non-reactive low friction plastic material such as polytetrafluoroethylene. A first end 42 is fixed to the body 30, while a second end 44 houses the net for independent deployment and retrieval.
[0031]
The net actuator 24 is adapted to reciprocate the deployment and retrieval assembly in the body and introducer to operate the net 20. The actuator 24 includes a first handle 50 fixed to the body 30 and a second handle 52 attached to the deployment and retrieval assembly 28 and movable with respect to the handle 50.
[0032]
A second handle 52 is fixed to the assembly 28 and mounted on the handle 50 between its ends for longitudinal sliding. The second handle includes a two finger ring member 80 slidable on the handle 50. The handles 50, 52 as shown are formed from a molded plastic material.
[0033]
The deployment and retrieval assembly 28 is configured to transmit substantial deployment and contraction forces to the net while allowing the scope body to be freely manipulated and bent to position the net at a desired location. And are located. The assembly 28 includes a link including a first link 70 and a second link 71 connected to the actuator 24 for transmitting compressive and tensile forces between the handle 52 and the bore 58. Bore 58 is located in the center of body 30. The link 70 transmits a relatively substantial compressive force without bending or breaking. The illustrated first link portion 70 is formed from a hypodermic needle material, i.e., is a cylindrical stainless steel tube. The second link 71 as shown is a multi-strand cable. The first link unit 70 couples with the second link unit 71 when the link comes off the main body 30.
[0034]
The link 71 extends from the body 30 into the introducer 40 so that it must be flexible but still transmit compressive and tensile forces to the introducer. The illustrated link 71 is tightly surrounded by the passage of the body of the passage 40 of the introducer. The link 71 is relatively stiff compared to the flexible introducer. When transmitting a compressive force, the link 71 elastically deforms and curves against the introducer wall. Link 71 has good compressive and tensile strength and is somewhat elastically bendable. The link 71 will bend somewhat without bends and kinks.
[0035]
The first connector 80 and the second connector 82 fix the loop 22 at two positions with respect to the net 20. The proximal side of the net is tied at a location 85 between the loop cables. As shown in FIG. 3, a tether 27 is used to tie the proximal side of the net. This tether is shorter than a conventional tether over the entire length of the introducer. Although additional net attachment techniques may be used in the practice of the present invention, no additional tether systems are required.
[0036]
Referring now to FIG. 3, a first connector 80 structurally couples the link 71 and the loop 22 together. The illustrated connector 80 is a short tube crimped to both ends of the loop 22 and to the second link 71. The illustrated connector tube is crimped around the loop and link to form a rotatable cross-section within the introducer 40. The illustrated connector 80 is formed of a hypodermic needle material like the first link part 70. The second connector 82 further mates an opposing portion on the net loop 22 at a position proximal to the net 20 with respect to the first connector 80.
[0037]
In the embodiment shown, the spacing between the two loop cables is used to secure the net element 21 to the link 71. An intermediate region R between the first connector 80 and the second connector 82 in the introducer 40 in the axial direction, represented in FIG. 3, may be used. In the exemplary embodiment, the proximal side of the net element 21 with respect to the support system 12 is secured to the net loop 22 at a convenient location 85. Suture material, or other known suitable methods, may be used to tie the net to the loop.
[0038]
The net 20 is deployed from the introducer second end 44 and manipulated by the surgeon to catch the severed tissue with the net and trap the tissue for retrieval from the subject. The net 20 can be deployed after a snare or similar technique has cut the target tissue. The net 20 includes a bag-like net element 21 slidably supported on a loop 22.
[0039]
The illustrated net loop 22 is formed from a thin wire loop configured and arranged to deploy and retract the net 20 in cooperation with the introducer. The illustrated loop 22 is a hard, resilient, flexible wire having its respective ends crimped in place at two locations by first and second connectors 80,82. When the net is deployed from the end of the introducer, the loop resiliently extends to a relaxed state where the loop width is substantially greater than the diameter of the introducer. The deployed snare is guided to a location containing the target polyp or other tissue. The net is contracted by the surgeon. When the net is retracted into the introducer second end 44, the loop resiliently pushes the introducer wall to elastically collapse, narrowing the loop protruding from the introducer. Tissue or other objects trapped within the net element 21 are increasingly limited by the elastic nature of the net and preserve the structure of the object when the net is pulled towards the distal end of the introducer. Or it allows objects of a wide range of sizes to be accommodated in the net without compromising safety.
[0040]
The net element 21 is a very light bladder-like structure having a net loop wire extending through its surrounding mesh, which forms a slidably supported net mouth and a hanging bladder on said loop. . The fibers of the net are very thin but still strong enough so that when the net loop is withdrawn, the net element slides along the loop wire away from the connectors 80, 82 and the net becomes The tissue within the bladder may be entrapped when collected and / or the entire net may be accommodated at the end of the distal net loop. The net has a minimum bulk so that when an empty net is retrieved, it can move completely easily into the passage of the introducer.
[0041]
The illustrated net is formed from 100% nylon fibers having a strand diameter of about 0.0125 mm to 0.04 mm. The fibers are woven in a diamond mesh pattern with mesh strands separated by 1 mm to 3 mm, and their intersections are fixedly tied together. The net material shown is substantially similar to that of a fine mesh hair net. The net is formed by cutting a net of approximately square, circular or elliptical portion, trimming or otherwise finishing the ends, and threading the loop wire through the surrounding mesh element. The size of the cut net portion is selected to be larger than the area of the net loop sufficiently to ensure that the bag-shaped tissue collection portion hangs from the mouth of the net. It is not large enough to cause difficulty in packing the net when pulled in.
[0042]
Attempting to completely retrieve the net containing tissue in the introducer 40 may result in tissue loss due to pushing the tissue through the net. The net fibers are thin and strong, they cut the tissue or they break down, and neither of these options is desirable. The thumb ring of the net actuator may include a tag (not shown) to warn the surgeon not to continue withdrawing the net against unusual resistance.
[0043]
The present invention solves the problems faced by surgeons and nurses using some prior art designs. Nurses and physicians have had difficulty understanding the operation of the tether, especially the interaction of the ring and post. Thus, from time to time, the device is incorrectly operated and malfunctions. The design of the present invention allows a nurse to push back on the handle to conveniently pack the net inside the introducer passageway.
[0044]
Further, the surgeon often needs to operate the endoscope to a location in an interior area that is difficult to access. Certain procedures require the endoscope to bend or twist. The area of the endoscope that is twisted or bent is called the joint area.
[0045]
Some net devices feature a multi-connector design in which the connectors are spaced somewhat closer to the second end 44. In these designs, multiple connectors on the net device resisted bending of the scope. In addition, the resulting friction makes it difficult to deploy the net once the scope has been brought into the desired state by the surgeon. One advantage of the present invention is the increased freedom of movement within the joint area and the ease of net deployment.
[0046]
During operation of system 10, the surgeon experiences increased ease of use over prior art designs. In the embodiment shown, the joint area (A) defined along the longitudinal axis of the introducer 40 during deployment of the net element₁, A_TwoThe first connector 80 is axially spaced from the second connector 82 such that there is only one connector within the first connector 80. In the illustrated system, the first connector 80 is located at least 6 inches from the second connector 82.
[0047]
The articulation region defines an axial portion of the introducer 40 that is substantially non-linear. The joint area typically includes a bend greater than 30 ° and can exceed 200 ° with a radius of 0.75 inches or less.
[0048]
Referring to FIG. 4, a portion of the system 10 is illustrated as being in an expected shape within the subject. During operation of the scope, the surgeon may operate the introducer second end 44 into a sharp bend. At times, the second end may be bent up to 180 ° as illustrated in FIG. Deployment of the net 20 in this and similar states is difficult if both connectors 80, 82 are within the joint area. The combined dynamic frictional force of each connector against the inside of the introducer passageway makes deployment of the net otherwise difficult. As illustrated in FIG. 4, the surgeon can more easily deploy the net in various states.
[0049]
A second aspect of the present invention is illustrated by the drawings. A portion of an endoscopic surgical device 10 for retrieving cut tissue and or foreign material from within a subject is illustrated in FIGS. In the illustrated design, device 10 includes support unit 12 and net actuator 24 as described above. However, another configuration of the net deployment and retrieval assembly 28 is utilized.
[0050]
In the illustrated design, the net deployment and retrieval assembly 28 uses a single connector. Referring now to FIG. 5, a connector 182 structurally couples the link 71 and the loop 22 together. The illustrated connector 182 is a short tube that is crimped to both ends of the loop 22 and to the second link 71. The connector tube shown is crimped around the loops and links to form a rotatable cross-section within the introducer 40. The illustrated connector 182 is formed of a hypodermic injection needle material similarly to the first link portion 70.
[0051]
One goal of the design is to reduce the amount of hard material in the joint area. During operation of the system 10, the surgeon experiences ease of use beyond prior art designs. As shown in FIG. 6, the joint area (A) defined along the longitudinal axis of the introducer 40₁, A_TwoThe length of the hard material within (bounded by) is minimized during operation of the net element. The reduction in hard material results from reducing the length of the loop cable 22 in the joint area.
[0052]
As shown in FIG. 5, the proximal side of the net element 21 relative to the support system 12 is fixed to the net loop 22 at a convenient location 185. Suture material, or other known methods, may be used to tie the net to the loop. As shown in FIG. 5, a tether 27 is used to tie the proximal side of the net. This tether is shorter than a conventional tether over the entire length of the introducer member. Tether 27 may be tied close to the shoulder of connector 182. As shown, the tether has a diameter no greater than the shoulder thickness of the connector. Although additional net attachment techniques can be used in the practice of the present invention, no additional tether system is required.
[0053]
While two aspects of the invention have been illustrated and described in considerable detail, the invention is not to be considered as limited to the precise configuration disclosed. Various applications, modifications and uses of the invention may occur to those skilled in the art to which the invention pertains. It is intended to cover all such adaptations, modifications and uses that fall within the scope or spirit of the appended claims.
[Brief description of the drawings]
[0054]
FIG. 1 is a front view of a surgical device constructed in accordance with one aspect of the present invention, illustrating a deployed net element.
FIG. 2 is a view similar to FIG. 1, illustrating the contracted net element.
FIG. 3 is a partially enlarged view of a portion of the apparatus shown in FIG. 1, showing details of the introducer member.
FIG. 4 is a partially enlarged view of a portion of the device shown in FIG. 1, depicting the device in an illustrative shape within a subject.
FIG. 5 is a partial enlarged view of a portion of a surgical device constructed in accordance with a second aspect of the present invention, showing details of the introducer member.
FIG. 6 is a partial enlarged view of a portion of the device illustrated in FIG. 5, depicting the device in an illustrative shape within a subject.

Claims (6)

An endoscopic surgical device for recovering a cut tissue or foreign body from a human body, the device comprising:
a. A support unit,
i. A body defining a first passage therethrough; and ii. An elongate introducer member having a first end proximal and fixed to the body, and a second end remote from the body, the elongate introducer member comprising the first introducer member; A support unit including an introducer member aligned with the passage and defining a second passage open at said second end; and b. A tissue collection net system,
i. A net comprising a wire-like elastic loop and a net element having a mouth and a tissue collection bag slidably disposed on said loop, said loop terminating with two mutually parallel loop cables; A net positioned proximate the second end for deployment and contraction through the opening of the second passage;
ii. A net deployment and retrieval assembly extending substantially through the first and second passages and connected to the net, the assembly including a motion transmitting member extending into the second passage to the loop. And iii. A first handle fixed to the main body, and a second handle fixed to the motion transmitting member and movable with respect to the first handle, wherein the second handle is the first handle. Moving relative to, including a tissue recovery net system including a net actuator unit that will move the net into and out of the opening of the second passage,
c. The second passage of the introducer member has a diametric dimension, when deployed, substantially less than the width of the loop, the member engaging the loop at the opening at the second end. Mating, and as the net contracts and moves into the passage of the introducer member, the loop resiliently collapses and expands, and the loop, when deployed, assumes its uncollapsed shape. Elastically return,
d. The net system further includes a first connector, a second net connector proximate the second passage opening, and an axial spacing of the loop cable between the first connector and the second connector. A defined intermediate portion, wherein the first connector and the second connector are adapted to fasten each loop cable, and an end of the net element includes the first connector and the second connector. A device tied to the loop in an intermediate loop between the second connector. The deployment and retrieval assembly includes a thin, flexible, wire-like motion transmission member between the net actuator unit and the loop, the motion transmission member extending within an introducer guideway, wherein the introducer guideway is 2. The apparatus of claim 1 wherein said motion transmitting member is closely surrounded and forces said member to translate axially within said passage. The apparatus of claim 1, wherein the first connector is positioned at least 6 inches from the second connector, such that during deployment of the net element, only one connector is in the articulated area. An endoscopic surgical device for recovering a cut tissue or foreign body from a human body, the device comprising:
a. A support unit,
i. A body defining a first passage therethrough; and ii. An elongate introducer member having a first end proximal and fixed to the body, and a second end remote from the body, the elongate introducer member comprising the first introducer member; A support unit including an introducer member aligned with the passage and defining a second passage open at said second end; and b. A tissue collection net system,
i. A net comprising a wire-like elastic loop and a net element having a mouth and a tissue collection bag slidably disposed on said loop, said loop terminating with two mutually parallel loop cables; A net positioned proximate the second end for deployment and contraction through the opening of the second passage;
ii. A net deployment and retrieval assembly extending substantially through the first and second passages and connected to the net, the assembly including a motion transmitting member extending into the second passage to the loop. And iii. A first handle fixed to the main body, and a second handle fixed to the motion transmitting member and movable with respect to the first handle, wherein the second handle is the first handle. Moving relative to, including a tissue recovery net system including a net actuator unit that will move the net into and out of the opening of the second passage,
c. The second passage of the introducer member has a diametric dimension, when deployed, substantially less than the width of the loop, the member engaging the loop at the opening at the second end. Mating, and as the net contracts and moves into the passage of the introducer member, the loop resiliently collapses and expands, and the loop, when deployed, assumes its uncollapsed shape. Elastically return,
d. The net system further includes a connector, wherein the connector is adapted to fasten each loop cable, and an end of the net element is disposed on the proximal side of the connector with respect to the support unit. A device associated with the motion transmitting member. The deployment and retrieval assembly includes a thin, flexible, wire-like motion transmission member between the net actuator unit and the loop, the motion transmission member extending within an introducer guideway, wherein the introducer guideway is 5. The apparatus of claim 4 wherein said motion transmitting member is closely surrounded and forces said member to translate axially within said passage. 5. The apparatus of claim 4, wherein an end of the net element is tied to the motion transmitting member proximate a shoulder proximal of the connector with respect to the support unit.